Fix zip source double free in fs_zip_dir

[trufae]

Motivation

• Prevent a double free/use-after-free when enumerating untrusted ZIP contents caused by freeing a zip_source_t after ownership was transferred to libzip via zip_open_from_source() in libr/fs/p/fs_zip.c.

Description

• Remove the extra zip_source_free(zs) call after zip_close(za) in fs_zip_dir() so ownership semantics match libzip's zip_open_from_source() behavior.

Testing

• Ran repository checks including git diff --check, viewing the git diff for libr/fs/p/fs_zip.c, and git status --short, and committed the change; all commands completed successfully.

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Codex Task